Static dissipating plastic truck cargo bed liner

ABSTRACT

A pickup truck cargo bed liner is disclosed which is vacuum formed of unitary plastic and adapted to fit within and protect the contours of a pickup truck cargo bed. An electrically conductive plastic film material is co-formed with and integrally adhered to the plastic forming the liner to provide an electrically conductive film thereon for preventing and dissipating static electricity buildup on the liner surface. Conductive means provide an electrically conductive contact between the conductive plastic film and a normally grounded portion of the vehicle.

FIELD OF THE INVENTION

[0001] This invention relates to molded plastic protective liners forpickup truck cargo beds.

BACKGROUND OF THE INVENTION

[0002] Pickup trucks have been used for many years as working vehicles.In recent years pickup trucks have become increasingly popular as familytransportation vehicles, because of their dual ability to haulpassengers and cargo. The cargo bed surfaces of pickup trucks aregenerally finished with paint by the manufacturer. If the paintedsurfaces are unprotected, they can be scratched from cargo impact ordeteriorated by weather or corrosives, seriously detracting from thevalue of the trucks. Whether a pickup truck is used as a working vehicleor as a family transportation vehicle, it is important to keep thesurface of the cargo bed in satisfactory condition.

[0003] Various cargo bed liners used to protect the surface of cargobeds are described in prior art patents. One piece molded plastic truckliners comprising a front wall, opposing side walls and a bottom wallare shown in U.S. Pat. Nos. 4,592,583 to Dresen, et al., 4,341,412 toWayne, 4,336,963 to Nix, et al., 4,181,349 to Nix, et al., 4,047,749 toLambitz, and 3,814,473 to Lorenzen. All of the above patents show moldedplastic liners which in practice have usually been thermoformed fromhigh density polyethylene which has excellent strength, toughness anddurability, and will withstand the normal expected weather extremes towhich a pickup truck likely is exposed in normal use.

[0004] During the past 15 years in excess of 10 million unitary moldedplastic bed liners have been sold and installed in pickup trucks in theUnited States. Plastic bed liners have in that period become one of themost common OEM and after market accessories purchased by pickup truckowners to protect the value of their pickup trucks. Very recently it hasbeen reported that in a handful of cases, explosions have occurred whilegas cans resting on plastic surfaces were being filled with gasoline.While the causes of such explosions have not been established, it hasbeen theorized that such explosions have been caused or may be caused inthe future by the build up of static electricity during refueling of gascontainers resting on plastic bed liners.

[0005] Therefore, a need is perceived to provide a one-piece plasticprotective cargo bed liner which will prevent and dissipate staticelectricity buildup on the liner surface.

SUMMARY OF THE INVENTION

[0006] The present invention is summarized in a protective moldedplastic truck bed liner formed from the preferred high densitypolyethylene plastic material and having an integral electricallyconductive surface. The truck bed liner may be formed with all of thefeatures of existing bed liners, and retains all of the strength,toughness, resilience and durability which have made molded plastic bedliners so popular with pickup truck owners. A selected thermoplasticmaterial having an electrically conductive material incorporated thereinis co-formed with the upper surface of the plastic forming the liner toprovide a conductive film thereon, the conductive film being in the formof a plastic integrally adhered to the liner upper surface.

[0007] It is an object of the present invention to provide a plastictruck cargo liner having an integral, durable static dissipatinginterior surface.

[0008] It is a further object of the present invention to provide aplastic protective truck cargo liner having a bottom wall with adurable, conductive surface and means for connecting the conductivesurface to the surrounding metal truck bed in electively conductiverelation.

[0009] It is a further object of the invention to provide a plasticprotective truck cargo liner having a conductive film of plastic withconductive material incorporated therein integrally adhered to the linerupper surface.

[0010] It is an additional object of the invention to provide a plasticprotective truck cargo liner having a conductive film of plasticintegrally adhered to at least a portion of the liner upper surface indimensionally stable relation.

[0011] Further objects, features and advantages of the invention will beapparent from the following detailed description when taken inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012]FIG. 1 is a perspective view of a cargo bed liner of the presentinvention installed in a pickup truck.

[0013]FIG. 2 is a fragmentary sectional view taken substantially alongline 2-2 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0014]FIG. 1 illustrates a conventional pickup truck 10 having a cab 12and a truck cargo bed 14. A preferred embodiment of the protective cargobed liner 16 of the invention is installed within the truck cargo bed14.

[0015] The truck bed liner 16 is formed in a conventional manner of highdensity polyethylene in a single, integral unit, and has a liner bottomwall 18 which is adapted to fit on and substantially cover the fullwidth of the truck cargo bed floor. The liner bottom wall 18 willnormally have a width substantially as great as the distance between thetruck side rails. As shown in FIG. 2, the liner bottom wall 18 containsa plurality of separate, inverted U-shaped longitudinal corrugations 22.

[0016] The truck bed liner 16 also has two liner wheel wells 24 formedin the liner bottom wall 18 at opposite sides thereof. The liner wheelwells 24 are adapted to accommodate the truck cargo bed rear wheel wells(not shown).

[0017] A liner front wall 34 is connected to and extends upwardly fromthe liner bottom wall 18. Two liner side walls 42 are connected to theliner bottom wall 18 and wheel wells 24 and also the liner front wall 34at opposite sides thereof. The side walls 42 each have an upper margin44 which is preferably adapted to fit flush against the cargo bed wall46.

[0018] As shown in FIG. 2, the side walls 42 may preferably have one ormore protrusions 86 at their upper margins 44 which protrude inwardly toengage an adjacent truck bed surface beneath the truck cargo bed siderail 48, to effectively maintain the adjacent portions of the linerupper margin 44 snugly against the cargo bed wall 46 beneath the truckside rail 48.

[0019] Another preferred form of truck bed liner (not shown), of thetype generally shown in U.S. Pat. No. 4,341,412 to Wayne, has side wallswhich extend upwardly inside the truck cargo bed side rails, and flangeswhich extend outward over the tops of the truck rails to cover andprotect the rails. This invention is equally useful with bothunder-the-rail and over-the-rail bed liner side wall designs as thosedesigns are generally known to the bed liner industry.

[0020] The inside working surfaces 54 of the cargo bed liner of thepresent invention are provided with an integral conductive film 84 ofmaterial. Such a film of material will dissipate and prevent build up ofstatic electricity from the working surface to any portion of thesurrounding grounded truck cargo bed to which it is conductivelyconnected or in conductive contact. The film 84 may be advantageouslyprovided by laminating the film to the upper surface of the high densitypolyethylene sheet during extrusion forming of the sheet prior to vacuumforming the liner from the sheet. Suitable materials capable of beingbonded to polyethylene and providing such a conductive surface includepolyethylene, the preferred material, and other thermoplastic materialswell known to the plastics and thermoforming industries. The disclosureof U.S. Pat. No. 4,693,507 to Dresen, et al., incorporated herein byreference, discloses a suitable co-extrusion process. The thickness ofthe co-extruded film surface may be selected and varied to produce theoptimum combination of forming conditions and performance in use.

[0021] The surface film material may be formed of the preferredthermoplastic material containing an effective portion of anelectrically conductive material such as graphite fibrils, carbon blackmetal powder or filaments, or the like. The particular concentration ofthe electrically conductive material in the thermoplastic material willbe selected to optimize performance, cost and forming considerations.

[0022] The surface film material may also be selected to optimize theappearance of the exposed film surface, as well as other surfacecharacteristics such as co-efficient of friction.

[0023] By incorporating conductive material only in the thin surfacefilm of the bed liner, the inherent characteristics of the polyethylenebed liner substrate will be substantially unchanged from the currentlypopular polyethylene bed liner. Whatever additional cost is incurredfrom the addition of the selected electrically conductive material isminimized because the conductive material is only incorporated in thethin film, not the entire thickness of the bed liner substrate. Whateveradditional stiffness or rigidity is imported to the film by theconductive material will not unduly affect the flexibility orformability of the underlying bed liner substrate.

[0024] As indicated above, conductive means must be provided to conductstatic electricity from the liner conductive film working surface to thesurrounding metal truck cargo box. Preferred conductive means are theprotrusions 86 in the upper margin 44 of the preferred bed linerunder-the-rail side walls 42 shown in FIG. 2. Several such protrusions86 pressed against the steel material beneath the truck rails 48 wouldlikely insure that the liner conductive surface film 84 would remainconductively engaged with the grounded truck cargo box in all useconditions.

[0025] Other conductive means, such as metal screw fasteners 88 andrivet type metal contacts 90 extending from electrical contact with thesurface film 84 through the liner substrate material to a metal contactor flexible strap contact 92 which will maintain electrical contact withthe underlying truck cargo box floor, are illustratively shown in FIG.2, although it should be understood that normally only one such type ofillustrated conductive means would be used (though several of theselected conductors could be employed to achieve redundancy underadverse use conditions).

[0026] The film of any of the above materials may also be caused toadhere to the polyethylene surface by conventional use of adhesives or athermal attachment process before or during the vacuum forming of theliner.

[0027] As suggested above, the unitary plastic liner 16 is preferablyformed in a mold from a sheet of heated polyethylene by a conventionalthermoforming process. In that process, the thermoforming vacuum mold isa one-sided mold having vacuum ports provided therein to draw the heatedsheet of material against the mold. The polyethylene sheet from whichthe liner is formed is conventionally made by heating a quantity ofpellets of polyethylene until the heated material becomes liquified andof suitable viscosity, extruding the material though an extrusion dieand forming rolls which lay the extruded material out in a sheet ofdesired width and thickness, and cooling the sheet. The cooled sheet isthen cut into planar blanks of desired size from which the truck bedliners will be formed.

[0028] In carrying out the present invention, a thin film of conductivethermoplastic material as previously described is preferably co-extrudedwith a polyethylene substrate in a conventional manner to form a sheetof polyethylene having a film of approximately 25 to 30 thousandths inchthick, or such other thickness as is found optimal, on one side thereof.During such co-extrusion the heated polyethylene substrate material andthe similarly heated thermoplastic film material with incorporatedelectrically conductive material mixed therein are maintained at properviscosities in accordance with conventional co-extrusion techniques tocause the materials to flow together evenly and form molecular bondsbetween the film material and the substrate material.

[0029] When a film is used which substantially resembles the substratesheet material such as high density polyethylene, it is possible toco-extrude (or laminate during extrusion) the film on less than all ofthe substrate sheet material, without adverse visual effects.Accordingly, the film 84 may be centered on the substrate sheet and ofsufficient width only to cover all portions of the sheet that are formedinto the liner bottom wall 18, since the bottom wall 18 is the potion ofthe liner on which a static dissipating surface is most advantageous.Because portions of the sheet will be drawn in unequal amounts duringthermoforming due to irregularities in the liner design, particularlynear the comers between the liner front wall 34 and side walls 42, andnear the liner wheel wells 24, the edges of the film 84 may be quiteirregular on the liner 16. If the conductive film 84 has the sameappearance as the underlying liner inside surface 54, the irregular edgeof the film 84 will not be readily visible nor objectionable. Limitingthe film 84 to only the width necessary to cover the liner bottom wall18 will obviously result in material savings and reduction of costs,without loss of effective static dissipation performance. Alternatively,the film could be limited to only a portion of the liner bottom wall, ifcost considerations require. In that case, a fueling area could beformed and/or marked on the bottom wall to warn and encourage users toconfine fuel storage, transporting, and handling of fuel containers tothat portion of the bottom wall surface.

[0030] A separate one-piece tailgate liner 72 may also be attached tothe tail gate of the truck in a conventional manner. The tailgate liner72 may also advantageously include the conductive static dissipatingfilm 84, and conducting means such as fasteners 88 or other suitablemeans for conductively connecting the film 84 to the grounded steeltruck tailgate.

[0031] While the conductive film 84 has been illustrated and describedon a preferred plastic truck body liner, it is understood that theanti-slip frictional film of the invention may be incorporated inthermoformed plastic truck bed liners of any desired shape or style. Ifis also understood that the invention may advantageously be employed inliners for sport utility vehicles and passenger vans and mini-vans,wherein fuel containers may be transported and handled.

[0032] It is understood that the invention is not confined to theparticular construction and arrangement of parts herein illustrated anddescribed, but embraces all such modified forms thereof as come withinthe scope of the following claims.

What is claimed is:
 1. A receptacle for a cargo vehicle comprising, incombination, a pair of sidewalls, a front wall, a bottom panel joiningsaid sidewalls and said front wall, and said receptacle made of athermoplastic material, at least a portion of said thermoplasticmaterial including dispersed electrically conductive material.